feat: add session idle timeout cleanup goroutine

- Periodic cleanup loop deletes stale clients based on SESSION_IDLE_TIMEOUT
- Orphaned sessions (no clients) are cleaned up automatically
- last_seen already updated on each authenticated request via GetSessionByToken

internal/handlers/handlers.go

@@ -7,6 +7,7 @@ import (
 	"errors"
 	"log/slog"
 	"net/http"
+	"time"
 
 	"git.eeqj.de/sneak/chat/internal/broker"
 	"git.eeqj.de/sneak/chat/internal/config"
@@ -30,12 +31,15 @@ type Params struct {
 	Healthcheck *healthcheck.Healthcheck
 }
 
+const defaultIdleTimeout = 24 * time.Hour
+
 // Handlers manages HTTP request handling.
 type Handlers struct {
 	params        *Params
 	log           *slog.Logger
 	hc            *healthcheck.Healthcheck
 	broker        *broker.Broker
+	cancelCleanup context.CancelFunc
 }
 
 // New creates a new Handlers instance.
@@ -43,7 +47,7 @@ func New(
 	lifecycle fx.Lifecycle,
 	params Params,
 ) (*Handlers, error) {
-	hdlr := &Handlers{
+	hdlr := &Handlers{ //nolint:exhaustruct // cancelCleanup set in startCleanup
 		params: &params,
 		log:    params.Logger.Get(),
 		hc:     params.Healthcheck,
@@ -51,10 +55,14 @@ func New(
 	}
 
 	lifecycle.Append(fx.Hook{
-		OnStart: func(_ context.Context) error {
+		OnStart: func(ctx context.Context) error {
+			hdlr.startCleanup(ctx)
+
 			return nil
 		},
 		OnStop: func(_ context.Context) error {
+			hdlr.stopCleanup()
+
 			return nil
 		},
 	})
@@ -96,3 +104,78 @@ func (hdlr *Handlers) respondError(
 		status,
 	)
 }
+
+func (hdlr *Handlers) idleTimeout() time.Duration {
+	raw := hdlr.params.Config.SessionIdleTimeout
+	if raw == "" {
+		return defaultIdleTimeout
+	}
+
+	dur, err := time.ParseDuration(raw)
+	if err != nil {
+		hdlr.log.Error(
+			"invalid SESSION_IDLE_TIMEOUT, using default",
+			"value", raw, "error", err,
+		)
+
+		return defaultIdleTimeout
+	}
+
+	return dur
+}
+
+func (hdlr *Handlers) startCleanup(ctx context.Context) {
+	cleanupCtx, cancel := context.WithCancel(ctx)
+	hdlr.cancelCleanup = cancel
+
+	go hdlr.cleanupLoop(cleanupCtx)
+}
+
+func (hdlr *Handlers) stopCleanup() {
+	if hdlr.cancelCleanup != nil {
+		hdlr.cancelCleanup()
+	}
+}
+
+func (hdlr *Handlers) cleanupLoop(ctx context.Context) {
+	timeout := hdlr.idleTimeout()
+
+	interval := max(timeout/2, time.Minute) //nolint:mnd // half the timeout
+
+	ticker := time.NewTicker(interval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			hdlr.runCleanup(ctx, timeout)
+		case <-ctx.Done():
+			return
+		}
+	}
+}
+
+func (hdlr *Handlers) runCleanup(
+	ctx context.Context,
+	timeout time.Duration,
+) {
+	cutoff := time.Now().Add(-timeout)
+
+	deleted, err := hdlr.params.Database.DeleteStaleSessions(
+		ctx, cutoff,
+	)
+	if err != nil {
+		hdlr.log.Error(
+			"session cleanup failed", "error", err,
+		)
+
+		return
+	}
+
+	if deleted > 0 {
+		hdlr.log.Info(
+			"cleaned up stale clients",
+			"deleted", deleted,
+		)
+	}
+}